DevTools: Use JS symbols instead of strings for eligible events.

third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js

Index: third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
diff --git a/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js b/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
index 89f8c8804c2aa11d86e1bcb907fd97d715409c11..b8facd4b5b7118af9344a8c1028195e3b89c1bc6 100644
--- a/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
+++ b/third_party/WebKit/Source/devtools/front_end/workspace/UISourceCode.js
@@ -62,18 +62,16 @@ WebInspector.UISourceCode = function(project, url, contentType)
     this._messages = [];
 }
 
-/**
- * @enum {string}
- */
+/** @enum {symbol} */
 WebInspector.UISourceCode.Events = {
-    WorkingCopyChanged: "WorkingCopyChanged",
-    WorkingCopyCommitted: "WorkingCopyCommitted",
-    TitleChanged: "TitleChanged",
-    SourceMappingChanged: "SourceMappingChanged",
-    MessageAdded: "MessageAdded",
-    MessageRemoved: "MessageRemoved",
-    LineDecorationAdded: "LineDecorationAdded",
-    LineDecorationRemoved: "LineDecorationRemoved"
+    WorkingCopyChanged: Symbol("WorkingCopyChanged"),
+    WorkingCopyCommitted: Symbol("WorkingCopyCommitted"),
+    TitleChanged: Symbol("TitleChanged"),
+    SourceMappingChanged: Symbol("SourceMappingChanged"),
+    MessageAdded: Symbol("MessageAdded"),
+    MessageRemoved: Symbol("MessageRemoved"),
+    LineDecorationAdded: Symbol("LineDecorationAdded"),
+    LineDecorationRemoved: Symbol("LineDecorationRemoved")
 }
 
 WebInspector.UISourceCode.prototype = {